He had previously been EVENS.
This move coincides with a report in this week's issue of the Wrestling Observer Newsletter which pointed to Cena versus Undertaker being one of two matches that are - as of this moment - scheduled to take place in April. The other being Roman Reigns versus Brock Lesnar.
As you can see in the table above, The Undertaker has been descending since November after opening at 3/1 at the start of that month.
His isn't the only price to be cut since January 5th.
Batista has moved from 7s into 5/1 and Braun Strowman is now 8/1 from 10/1.
The news of The Undertaker versus John Cena being a potential match at WrestleMania has also had an impact on another market - the one where customers can predict which bout will be the main event of the evening.
The option to wager on 'Any Undertaker Match' closing out the show has now been cut from 3/1 to 2/1 within the week. It had initially been priced up at 10/1 in July.
With the selection lowering, the traders have increased 'Lesnar .vs. Reigns' from 1/10 into 1/5 as well as a few other match-ups.
News that Ronda Rousey and her agent met with Triple H on Tuesday night may have also forced the bookies to cut 'Any Women Match' from 5/1 to 7/2.